Binding sheets of paper into pads is generally accomplished by bonding or treating one edge of the sheets with a liquid adhesive using rollers or brushes and weights, and allowing the adhesive to dry or set, which can take hours or even days. To reduce the setting time, it is known to use solid, hot melt adhesives which can be heated to melt the adhesive and bind the sheets. Many methods heat the hot melt adhesive in a container and then apply the liquid adhesive to the sheets by dipping or immersion plates. More recent methods include placing a solid hot melt adhesive on a backing against the edge of the sheets to be bound and heating and melting the adhesive onto the sheets. Apparatus and methods using backed solid hot melt adhesives to bind conventional paper sheets are now common.
U.S. Pat. No. 3,531,358 to Rost discloses one such apparatus for binding stacked sheets. In Rost, the sheets are first jogged to align the edge to be bound, before being clamped. The jogging plate doubles as a hot plate and heats and melts a thermally flowable adhesive on a backing onto the edge of the sheets. The hot plate heats for twenty minutes. However, the adhesive is also disposed and melted onto the side of the outermost sheets, and the adhesive is placed underneath the sheets during binding. Additionally, there is no disclosure that this system can be used to bind carbonless forms. A binding system disclosed at page 112 of the Jan. 22, 1990 issue of Design News describes a similar heating and binding system.
Hoff, U.S. Pat. No. 3,616,074 is directed to a similar binding apparatus. In Hoff, the sheets of paper are indexed between three operating stations. In a first station, the sheets are clamped and jogged to align their edges. In the second station, a heating platen heats a backed sheet of hot melt material to the edges of the sheets. The adhesive is wrapped around and melted onto the sides of the sheets using additional heaters at the third station. However, the adhesive is placed underneath the sheets during binding and carbonless forms are not discussed.
U.S. Pat. No. 3,757,736 to Anderson discloses a semi-automatic bookbinder which uses a roll to coat a liquid hot melt adhesive onto the edge of a paper stack. The stack is clamped, vibrated to align the edge, and then rotated 180.degree. to a heating and bonding station. The edge is preheated before the adhesive is rolled on.
Decker, U.S. Pat. No. 3,717,366, Abildgaard et al., U.S. Pat. No. 3,532,363, and Waldeck, U.S. Pat. No. 3,930,082 are representative of a large body of art involving the binding of conventional stacks of paper into pads or books using solid, backed hot melt type adhesives. None of these patents discloses placing the adhesive on top of the sheets to facilitate binding. Additionally, there are no known teachings to use backless, solid, hot melt adhesives to bind a stack of paper.